This invention relates to a gunning composition for use in the steel industry for repairing and maintaining troughs, runners, ladles, spouts and other equipment used for containing and processing molten steel. The composition is intended for use primarily as a patching material, to be applied on surfaces using gunning processes well known in the iron and steel industry at temperatures of up to about 1000.degree. F.
The gunning composition of the invention can be prepared by mixing 60-75% by weight of a refractory base material, such as calcined clay, mullite, brown fused alumina, or tabular alumina, with 10-20% by weight of silicon carbide, 7-15% by weight of ball clay, and 4-8% by weight of a binder material which includes very fine silica particles (preferably colloidal) dispersed in water. Between 5-10% by weight of a graphite material may optionally be included as a nonwetting agent and to inhibit the chemical reaction between "slag" (present in molten steel) and the refractory base material.
The use of a silica binder represents an improvement over known gunning compositions which utilize petroleum pitch or clay. The silica binder imparts several advantages to the gunning composition including (1) better adhesion to surfaces, particularly those containing carbon, (2) less cracking during evaporation of the water, (3) improved strength, and (4) increased resistance to oxidation, corrosion and erosion.